Browser Identification

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When web browsers connect to websites, they send a user agent, which identifies the browser and the
- rendering capabilities it possesses. They website can use this information to decide which version of the
- website to send to the browser. For example, many websites have different versions for desktop and
- mobile browsers.

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By default, Privacy Browser uses the built-in user agent that comes with the WebView installed on the
- device. You can see what it is by going to the Settings screen and setting the User
- agent to WebView Default. The screenshot below shows a Nexus 6P running Android 6.0.1
- with Android System WebView 51.0.2704.81 installed.

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There is enough information in the user agent that sometimes only a few visitors to a website will be the same. If the user agent
- is combined with another piece of non-unique identifying information, often it results in a unique fingerprint.
- The Electronic Frontier Foundation created a tool called Panopticlick
- to demonstrate how much information can be gleaned from these sources. If this test is run with JavaScript enabled the
- amount of information that is disclosed increases greatly. Browser Leaks and
- Am I Unique are also good sources of information.

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Privacy Browser allows you to change the user agent. There are several preset options that match common browsers and operating systems.
- Privacy Browser defaults to its own user agent, which is simply PrivacyBrowser/1.0. For tracking purposes, anything that is rare is easier
- to track. If Privacy Browser becomes common and many people use PrivacyBrowser/1.0 as their user agent, it will be a good choice for privacy.
- Firefox or Chrome are the most common user agents, but they auto-update and their version numbers change so quickly
- that it is likely the user agents included in Privacy Browser will often be out of step with the majority of user agents in the
- server logs.

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A second reason to change the user agent is to convince the web server to send the desktop version of the web page, which often works
- better on modern smart phones than the mobile version. For this purpose, PrivacyBrowser/1.0 works well, because web servers typically
- default to the desktop version unless they recognize a phone browser agent.

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Android's WebView does not allow the user agent to be blank. If it is, WebView simply sends the default user-agent to the server.